Neurons and Synaptic Transmission Flashcards
Why is neural activity considered an electro-chemical process?
It involves both electrical and chemical elements.
What is the electrical part of neural activity?
The flow of ions (charged particles) in/out of the cell, or through the cell
What is the chemical part of neural activity?
The flow of neurotransmitters between neurons
What are the key ions involved in neurons?
Sodium - Na+
Potassium - K+
Chloride - Cl -
What is a resting membrane potential?
When the neuron is not firing
The difference in charge across the membrane at equilibrium is about -70mV
How many Na+ and K+ ions are inside/outside the neuron at its resting membrane potential?
Inside: More K+ and less Na+
Outside: More Na+ and less K+
*Think of the inside as “less positive” instead of “more negative”.
What are the three stages of computation in the neuron?
Stage 1 - Input Stage
Stage 2 - Processing Stage
Stage 3 - Output Stage
What is a synapse?
Where the axon of one neuron connects to the dendrites of another neuron
Presynaptic Neuron
The neuron BEFORE the synapse
Postsynaptic Neuron
The neuron AFTER the synapse
Synaptic Cleft
Another name for the synapse
How neurons send signals (steps)
- An action potential arrives at the terminal buttons.
- There are vesicles holding neurotransmitters in the terminal button areas of the presynaptic neuron
- These vesicles dock to docking proteins, fuse with the presynaptic membrane, and are dumped into the synapse
- Empty vesicles are recycled through endocytosis of the clathrin-coated pit to take up more neurotransmitters and restart the cycle
How neuron receive signals (steps)
- Neurotransmitters in the synapse dock onto certain ion receptor to either open or close channels
- For an action potential, Na+ channels open and let Na+ into the cell.
- Na+ is positive, and the neuron starts to become excitatory
- Enough of these excitatory postsynaptic potentials add up at the axon hillock until the neuron is depolarized enough (-50mV) and triggers the next action potential to travel down the neuron’s axon
Excitatory Postsynaptic Potential (EPSP)
Cell is less polarized (depolarized) because it has less of a negative charge. This depolarization is excitation because it makes it more likely that the cell will reach the threshold to trigger an action potential. (-50mV)
Inhibitory Postsynaptic Potential (IPSP)
Cell can become more polarized (hyper polarized) so it has a more negative charge.
Hyperpolarization is inhibition because it makes it less likely that the cell will reach the threshold to trigger an action potential